Method for preparing catechol and hydroquinone

ABSTRACT

A mixture of catechol and hydroquinone is prepared by oxidizing phenol in an aqueous medium with hydrogen peroxide at a pH of 6.0 or lower in the presence of a catalyst consisting of at least one organic metal coordinate compound which is prepared from a salt of a metal selected from the class consisting of iron, copper, chromium and cobalt and an organic ligand compound selected from the class consisting of aromatic chelating compounds, heterocyclic monodentate coordinating compounds, heterocyclic polydentate chelating compounds and aliphatic chelating compounds, when one of the coordinate bonding groups in the aliphatic chelating compound is the carbonyl group, the remaining coordinate atoms or groups are other than the carbonyl group, and isolating the resulting catechol and hydroquinone from the oxidation admixture.

United States Patent Tahara et al.

[4 1 Nov. 18,1975

[54] METHOD FOR PREPARING CATECHOL AND HYDROQUINONE [75] Inventors:Susumu Tahara; ShigekiNagai;

Yurio Hayashi; Kou Hoshide; Shigenori Kawazoe; Katsuzo Harada; KoichiYamamoto, all of Ube, Japan [73] Assignee: Ube Industries, Ltd.,

Yamaguchiken, Japan [22] Filed: Mar. 13, 1974 [21] Appl. No.: 450,751

[30] Foreign Application Priority Data Mar. 23, 1973 Japan 48-32601 [52]US. Cl 260/621 G; 252/431 R; 252/431 C; 252/431 N [51] Int. Cl. C07C37/00 [58] Field of Search. 260/621 G; 252/431 R, 431 C, 252/431 N [56]References Cited UNITED STATES PATENTS 3,488,395 l/l970 Hooper 260/621 G3,531,519 9/1970 Parkin et a]. 260/621 G Gradeff 260/621 G Vesely260/621 G Primary Examiner-Norman P. Morgenstern Attorney, Agent, orFirmBurgess, Ryan and Wayne [57] ABSTRACT A mixture of catechol andhydroquinone is prepared by oxidizing phenol in an aqueous medium withhydrogen peroxide at a pH of 6.0 or lower in the presence of a catalystconsisting of at least one organic metal coordinate compound which isprepared from a salt of a metal selected from the class consisting ofiron, copper, chromium and cobalt and an organic li- 13 Claims, N0Drawings METHOD FOR PREPARING CATECHOL AND HYDROQUINONE The presentinvention relates to a method for preparing catechol (py'rocatechol,pyrocatechin or 1,2-dihydroxybenzene) and hydroquinone (hydroquinol or1,4- dihydroxybenzene), more particularly, it relates to a method forpreparing catechol and hydroquinone by directly oxidizing phenol withhydrogen peroxide.

in the known method wherein phenol is directly oxidized with hydrogenperoxide in the absence of metal ion, it is desirable that the reactionsystem contains substantially no or a very small amount of water. Theincrease in water content of the reaction system results in a noticeabledecrease in yields of catechol and hydroquinone. For example, if thereactionsystem contains 30% by weight of water, substantially nocatechol and hydroquinone are obtained. Under this circumstance, it isrequired that phenol be used in a large excess amount based on theamount of hydrogen peroxide used, or a non-aqueous solvent is used as areaction medium. Further, it is required that materials to be added tothe reaction system contain water in an amount as small as possible.These requirements for the above-mentioned method result in variouseconomical disadvantages, that is, low heat efficiency, undesirablenecessity of recovery of unreacted phenol, high cost of the non-aqueoussolvent and low yield of catechol and hydroquinone.

Further, it should be noted that the above-mentioned method requires theuse of a highly concentrated aqueous hydrogen peroxide solution, becausethe use of low concentration aqueous solution of hydrogen peroxidecauses low yields of catechol and hydroquinone and a low reaction ratein the oxidation of phenol. However, such a highly concentrated aqueoussolution of hydrogen peroxide is accompanied by a high risk of explosionduring handling.

I. Tanimoto, Bull. Chem. Soc. Japan, 43, 139 142 (l970), discloses thephenomenon that small amounts of catechol and hydroquinone are producedby oxidizing phenol with hydrogen peroxide in the presence of coppernitrate.

A. Chwala et al, J. Prakt. Chem. 152, 45 (1939), obtained catechol andhydroquinone by reacting, while cooling with ice, hydrogen peroxide withphenol in an excess amount with respect to that of hydrogen oxide, in aconsiderably diluted solution in the presence of ferrous sulfate over aperiod of 24 hours. However, the Chwala method which needs a very longreaction time is very disadvantageous from the point of view of economy.During the inventors studies of the Chwala method, it has been observedthat the oxidation reaction starts a long period of time after thecomplete mixing of phenol and hydrogen peroxide. This period of timeduring which the oxidation is not effected, is referred to as inductionperiod. Owing to the induction period, the Chwala method requires a verylong time, for example, 24 hours, to complete the oxidation of phenol.However, it is desirable that the oxidation is completed within a shorttime.

The object of the present invention is to provide a method for preparingcatechol and hydroquinone by directly oxidizing phenol at a high yieldwithin a short reaction time period.

The other object of the present invention is to provide a method forpreparing catechol and hydroqui- 2 none by directly oxidizing phenolusing a relatively low concentration of an aqueous hydrogen peroxidesolution.

The above object is accomplished by the method of the present inventionwhich comprises the steps of oxidizing phenol, to produce catechol andhydroquinone, with hydrogen peroxide in an aqueous medium at a pH nothigher than 6.0 in the presence of a catalyst consisting of at least oneorganic metal coordinate compound which consists of a metal componentselected from the group consisting of iron, copper, chromium and cobaltand at least one organic ligand component selected from the classconsisting of aromatic chelating compounds having at least twochelate-bonding atoms or groups, heterocyclic coordinating compoundshaving at least one coordinate-bonding atom or group and aliphaticchelating compounds having at least two chelate-bonding atoms or groups,when one of the chelatebonding group of said aliphatic compounds is acarbonyl group, the remaining chelate-bonding group is other than thecarbonyl group, and isolating the resultant catechol and hydroquinonefrom the oxidizing mixture.

The catalyst consisting of the organic metal coordinate compounds usablefor the method of the present invention may be prepared by bringing atleast one metal compound into contact with at least one organic ligandcompound in an aqueous medium in accordance with a conventional method.The metal compound usable for the preparation of the organic metalcoordinate compound may be selected from organic or inorganic acid saltsof iron, copper, chromium and cobalt, for example, chlorides, nitrates,phosphates, sulfates, carbonates, bicarbonates and carboxylates of theabove stated metals.

The aromatic chelating compounds usable for the preparation of thecatalyst are polydentate chelating compounds having at least twochelate-bonding atoms or groups and may be selected from the groupconsisting of, for example, catechol, salicylic aldehyde, salicylicacid, thiosalicylic acid, o-aminophenol, salicylic amide, o-nitrophenol,anthranilic acid, orthanilic acid, o-phenol sulfonic acid anda-nitroso-B-naphthol.

The heterocyclic coordinating compounds usable for the preparation ofthe catalyst are heterocyclic monodentate coordinating compounds whichhave only one coordinatebonding atom or group or heterocyclicpolydentate chelating compounds which have two or more chelate-bondingatoms or groups.

The heterocyclic monodentate coordinating compounds usable for thepresent invention may be selected from the class consisting of, forexample, pyridine, picolines, lutidines and quinoline.

The hetrocyclic polydentate chelating compounds usable for the presentinvention may be selected from the class consisting of, for example,nicotinic acid, nicotinic amide, isocinchomeronic acid, oz-thiophenicacid, o-phenanthroline, 2-mercaptopyridine, 2-aminothiazole,8-hydroxyquinoline, mercaptobenzothiazole and e-caprolactam.

The aliphatic chelating compounds usable for the present invention haveat least two chelate-bonding atoms or groups, when one of thechelate-bonding group is a carbonyl group, the remaining chelate-bondingatoms or groups are other than carbonyl group. The aliphatic chelatingcompounds may be selected from the class consisting of, for example,ethylenediamine, D,L-a-alanine, D,LB-alanine, 2,2',2"-trihydroxye- 3thylaminc, thioglycollic acid, thioacetamide thiourea,2,3-dimercapto-l-propanol, ethylenediaminetetraacetic acid,dimethylglyoxime, 2-hydroxyethylamine, ethylene cyanohydrin, oxamide,diethylene glycol, glutamic acid, lysine, methionine, glycine andarginine.

The reaction admixture wherein phenol is oxidized with hydrogen peroxideis prepared by mixing the or ganic metal coordinate compound and phenolwithin an aqueous medium and, then, admixing an aqueous solution ofhydrogen peroxide, or by mixing phenol with hydrogen peroxide within anaqueous medium and, then, admixing the organic metal coordinatecompound.

Phenol to be added may be in the state of solid, liquid or an aqueoussolution. Phenol in the reaction admixture is preferably in aconcentration of 0.2 to 30 mole, more preferably, 0.3 to mole based on1000 ml of water. Water in the reaction admixture may be suppliedtogether with phenol, hydrogen peroxide, the organic ligand compound,the metal compound or acid for adjusting pH or alone, into the reactionvessel.

Hydrogen peroxide to be added to the reaction system is preferably in anamount of 0.1 to 1 mole, more preferably, 0.15 to 0.8 mole with respectto 1 mole of phenol. Generally, hydrogen peroxide is added in the stateof an aqueous solution in a concentration of, preferably, to 60% byweight to the reaction system. The aqueous hydrogen peroxide solutionmay be added by drops or at once to the reaction system.

The amount of the organic metal coordinate compound to be present in thereaction admixture is adjusted in response to the types of metal andligand contained in the coordinate compound, reaction temperature andtime and concentrations of phenol and hydrogen peroxide. Generally, theorganic metal coordinate compound is used in an amount of 0.003 to 1mole, calculated in terms of the metal atoms in said compound, withrespect to 1 mole of phenol.

The absence of the organic metal coordinate compounds as specifiedhereinbefore in the reaction mixture results in substantially nooxidation of phenol. If the reaction is carried out in the presence ofonly a metal salt such as copper nitrate, instead of the organic metalcoordinate compound, catechol and hydroquinone is produced in a lowyield, and a very long time is necessary for the complete oxidation.

The reaction admixture is adjusted to a pH not higher than 6.0,preferably, of 1.0 to 5.0, by adding an aqueous solution of an inorganicacid, for example, hydrochloric acid, nitric acid, phosphoric acid orsulfuric acid, or organic acid, for example, benzene sulfonic acid ormethanesulfonic acid. The pH of the reaction admixture higher than 6.0causes low yields of catechol and hydroquinone.

The oxidation of phenol is preferably carried out at a temperature of 10to 80C, more preferably, 20 to 70C. An oxidation temperature lower than10C results in a low reaction rate and low yield of catechol andhydroquinone. Also, the oxidation of phenol at a temperature higher than80C causes an increase in the amount of undesirable byproducts.

The reaction admixture may be either in a homogeneous solution phase orin a heterogeneous system in which a portion of phenol is separated fromthe reaction solution due to its small solubility in water.

The aqueous hydrogen peroxide solution may be added by drops or at onceto the reaction system. When added by drops, the addition is carried outover a period of time, for example, 5 minutes, 10 minutes or more whilestirring. After the addition is completed the reaction admixture ispreferably stirred for a short time, for example, 3 to 30 minutes, inresponse to the type and amount of the catalyst used, concentrations ofphenol and hydrogen peroxide, and pH and temperature of the reactionadmixture.

After the complete oxidation of phenol, the resultant catechol andhydroquinone and the unreacted phenol are isolated from the reactionadmixture by way of extraction with an organic solvent, for example,methyl isobutyl ketone, n-butyl acetate and isopropyl ether, filtrationand, then, separation using a separatory funnel.

Catechol and hydroquinone may be separated from the unreacted phenol byway of distillation, and the unreacted phenol is recovered.

The extraction residue contains the organic metal coordinate compound,acid and water and is available for the next operation. That is, theorganic metal coordinate compound can be utilized for repeated oxidationoperations, for example, 10 or more oxidation operations.

The advantages of the method of the present invention are summarized asfollows.

1. The oxidation of phenol can be completed within a short time withoutthe induction period.

2. Catechol and hydroquinone can be produced at a high yield (based onboth the amounts of phenol and hydrogen peroxide used).

3. The oxidation conditions, pH and temperature, and type of the organicmetal coordinate compounds can be selected over a wide range.

4. The ratio of yield of catechol to that of hydroquinone can be easilycontrolled within a range from 0.5 to 3.0 by varying the oxidationconditions and the type of the catalysts.

5. There is no danger in handling the aqueous hydrogen peroxide solutionbecause low concentration of the aqueous hydrogen peroxide solutions canbe used for the method of the present invention.

6. The resultant catechol and hydroquinone can be easily isolated fromthe reaction admixture because the oxidation is carried out in anaqueous medium and, therefore, the products can be separated in aconventional manner, for example, extraction, filtration, separationusing a separatory funnel and distillation.

7. The extraction residue which contains the organic metal coordinatecompound, acid and water and the unreacted phenol can be recovered andre-utilized for the next operation. This is effective to preventcreation of pollution due to the process for producing catechol andhydroquinone.

The present invention will be illustrated in detail by the followingexamples.

EXAMPLE 1 An aqueous solution of a chelate compound was prepared byreacting 4.00 g (0.0l6 mole) of copper (l1) sulfate pentahydrate with0.0198 g (0.00018 mole) of catechol in 500 ml of water which have beenadjusted to a pH of 3.0 by adding a small amount of sulfuric acid, at atemperature of 50C. To the aqueous solution thus prepared were added 47g (0.5 mole) of phenol. 13.6 g (0.12 mole) of an aqueous solutioncontaining 30% by weight of hydrogen peroxide was added by drops, to theaqueous solution containing the chelate compound and phenol over aperiod of 10 minutes while stiring. and thereafter, the admixture thusprepared was stirred for minutes to oxidize the phenol and producecatechol and hydroquinone.

The reaction admixture was mixed with 1,000 g of methyl isobutyl ketoneto extract a mixture of the resultant catechol and hydroquinone andunreacted phenol from the reaction admixture. The extraction mixture wasseparated from the extraction residue containing the chelate compound inwater acidified with sulfuric acid. The extraction mixture was subjectedto distillation to isolate the resultant catechol and hydroquinone fromthe unreacted phenol and methyl isobutyl ketone. The yields of thecatechol and hydroquinone were determined by gas chromatography. Thedistillation product contained 3.97 g (0.0361 mole) of catechol and 2.88g (0.0262 mole) of hydroquinone. The ratio of the yield in moles ofcatechol to that of hydroquinone thus produced was 1.38. This ratio willbe referred to as yield ratio of catechol to hydroquinone hereinafter.The ratio of the sum of the yield in moles of catechol and hydroquinoneto the amount in moles of hydrogen peroxide used in the above-statedoxidation was 51.9%. The above ratio will be referred to hereinafter assum of yields of catechol and hydroquinone based on hydrogen peroxideused.

Additionally, the same procedures as mentioned above were repeatedexcept that after hydrogen peroxide was added by drops, the reactionadmixture was stirred for 5, 15, 20, 30 or 60 minutes. The yields of JEXAMPLE 2 The extraction residue obtained in Example 1 was used as anaqueous solution containing the chelating compound. 47 g (0.5 mole) ofphenol were added to the extraction residue and then, 13.6 g (0.12 mole)of 30% hydrogen peroxide was added at once to oxidize phenol and producecatechol and hydroquinone. The reaction admixture was stirred at atemperature of 50C for minutes. The resultant catechol and hydroquinonewere separated by the same procedure as in Example 1.

The same procedures as stated above were repeated 9 times, each usingthe extraction residue produced by the preceding reaction. Table 1 showsthe average yields in grams of catechol and hydroquinone, average yieldratio of catechol to hydroquinone, and average sum of the yields inmoles of catechol and hydroquinone with respect to the amount, in moles,of hydrogen peroxide used, in the 10 operations.

Table 1 Average sum of Average yield (g) Average yield yields ofcatechol EXAMPLES 3 AND 4 ln Example 3, the same procedures as inExample 1 were repeated using a chelate compound prepared 6 from 20 g(0.08 mole) of copper (ll) sulfate pentahydrate and 3.56 g (0.04 mole)of D,L-B-alanine. 1n Example 4, the same procedures as in Example 1 wererepeated ten times in the same manner as in Example 2. The results areshown in Table 2.

The same procedures as in Example 1 were repeated except that thechelate compound was prepared from 54.8 g (0.2 mole) of chromium (ll)sulfate heptahydrate and 0.88 g (0.00.8 mole) of catechol.

The results are shown in Table 3.

Table 3 Sum of yields of Yield (g) Yield catechol and ratio ofhydroquinone catechol to based on hydrogen Catechol Hydroquinonehydroquinone peroxide used (7:)

mole) mole) EXAMPLE 6 The same operations as in Example 5 were repeatedusing a commercial nicotinic amide copper (II) in an amount of 0.2 molecalculated in terms of the copper atom instead of catechol chromium(II).

The results are shown in Table 4.

Table 4 Sum of yields of Yield (g) Yield catechol and ratio ofhydroquinone catechol to based on hydrogen Catechol Hydroquinonehydroquinone peroxide used (71) mole) mole) EXAMPLE 7 The sameoperations as in Example 5 were repeated using copper (II) nicotinate inan amount of 0.1 mole calculated in terms of the copper atom instead o1"the catechol chromium (11).

Table 5 shows the results.

Table 5 Sum of yields of Yield (g) Yield catechol and ratio ofhydroquinone catechol to based on Catechol Hydroquinone hydroquinone H 0used (7:)

Table -continued Table 7 Sum of yields of Yield (g) Sum of yieldsEXAMPLES 8 THROUGH 12 In Example 8, 125 ml of an aqueous solution ofsulfuric acid with a pH of 3.0 was heated to a temperature of 45C. Atthis temperature, 1.1 g (0.0044 mole) of copper (11) sulfatepentahydrate and 0.0256 g (0.0002 mole) of a-thiophenic acid as a ligandwere added to the aqueous solution to prepare a coordinate compound,copper (ll) a-thiophenate. Thereafter, 14.2 g (0.106 mole) of an aqueoussolution containing 70% by weight of phenol was admixed with the chelatecompound aqueous solution. An aqueous solution of 30% by weight ofhydrogen peroxide in an amount of 3.0 g (0.0266 mole) was added bydrops, over a 5 minute period to the admixture prepared above, whilestirring and the reaction admixture was further stirred for 25 mminutesto produce catechol and hydroquinone. The resultant catechol andhydroquinone were isolated by the same operations as in Example 1.

The same operations as in Example 8 were repeated using, instead ofa-thiophenic acid, o-phenanthroline (Example 9), nicotinic amide(Example 10) ethylenediamine (Example 11) and pyridine (Example 12).

EXAMPLES 13 THROUGH 20 In Example 13, the same procedures as in Example1 were repeated using a coordinate compound prepared from 20 g (0.08mole) of copper (II) sulfate pentahydrate and 0.08 mole of pyridine, and15.0 g (0.16 mole) of phenol.

The same operations as in Example 13 were repeated seven times using,instead of pyridine, 0.08 mole of athiophenic acid (Example 14),o-phenenthroline (Example 15), salicylic aldehyde (Example 16),thiosalicyclic acid (Example 17), D,L-a-alanine (Example 18), 0.008 moleof ethylenediamine(Exam ple 19) and 0.08 mole of e-caprolactam (Example20).

The results are shown in Table 7.

of catechol and hydroquinone COMPARISON EXAMPLE 1 An aqueous solution of35% by weight of hydrogen peroxide was added by drops in an amount of0.028 mole calculated in terms of hydrogen peroxide, into an aqueoussolution of 0.5 mole of phenol, 0.006 mole of sulfuric acid and 0.004mole of phosphoric acid in ml of water at a temperature of 50C, whilestirring. The reaction admixture thus prepared was further stirred for 6hours at 50C. However, no catechol and hydroquinone were produced.

The same operations as stated above were repeated using 50 ml of water.No catechol and hydroquinone were observed in the reaction admixture.

COMPARISON EXAMPLE 2 Table 8 Yield (g) Sum of yields of catechol andhydro- Sampling quinone based on stage Catechol Hydroquinone H 0 used(72) 10 mins 0 0 0 20 mins 0 0 0 30 mins 0 0 O 40 mins trace 1.19 9.0

50 mins 1.37 2.22 27.2

60 mins 1.40 2.24 27.5

Table 8 shows that the yields of catechol and hydroquinone are very loweven 60 minutes after the start of the reaction. This means that theabsence of the catechol copper (11) at the start of the reaction resultsin a very low yield of catechol and hydroquinone even if catechol copper(I1) is produced at a later stage of the reaction.

EXAMPLE 21 The same operations as in Comparison Example 2 were repeatedexcept that 10 minutes after the addition of aqueous hydrogen peroxidesolutionwas completed, 0.00018 mole of catechol was added into thereaction admixture which contains copper sulfate (11), to preparecatechol copper (11) acting as the catalyst.

Portions of the reaction admixture were sampled at stages of 5, 10, 15and 20 minutes after the complete addition of the aqueous hydrogenperoxide solution, to determine the yields of catechol and hydroquinone.

The results are shown in Table 9.

10 ture and the ratio of the amount in moles of phenol to that ofhydrogen peroxide was 2 (Example 25) and 4 (Example 26).

Separately, the same procedures as in Example 22 were repeated threetimes except that the concentration of phenol was 23.9% based on theweight of the reaction admixture and the ratio of the amount in moles ofphenol to that of hydrogen peroxide was 2 (Example 27), 4 (Example 28)and 6 (Example 29).

10 Table 9 The results are shown in Table 10.

Table 10 Sum of yields of Yield catechol ratio and Concen- Yield (g) ofhydrotration Mole catechol quinone of ratio to based on Ex. phenolphenol/ Hydrohydro- H used No. (72) H 0 Catechol quinone quinone (72) 30Yield (g) Sum of yields of EXAMPLES 30 THROUGH 34 catechol and hydro-Sampling quinone based on stage Catechol Hydroquinone 11 0, used (7%)mins 0 0 0 mins 0 0 0 mins 3.90 2.24 46.5

mins 4.08 2.45 49.4

EXAMPLES 22 THROUGH 29 In Example 22, the same operations as in Example5 were repeated except that the chelate compound was prepared from 0.014g (0.00005 mole) of iron (11) sulfate heptahydrate and 0.02 g (0.000018mole) of catechol, the reaction admixture had a weight of 140 g, atemperature of 45C and a pH of 3.5, phenol was in a concentration of8.05% based on the weight of the reaction admixture, ratio of the amountin moles of phenol to that of hydrogen peroxide was 2, the aqueoussolution of hydrogen peroxide was added, by drops, into the reactionadmixture over a 5 minutes period, and after the addition of the aqueoushydrogen peroxide solution was completed, the reaction admixture wasstirred for minutes at 45C.

The same procedures as in Example 22 were repeated twice except that theratio of the amourt in moles of phenol to that of hydrogen peroxide was4 (Example 23) and 6 (Example 24).

Further the same procedures as in Example 22 were repeated twice exceptthat the concentration of phenol was 12.0% based on the weight of thereactionadmix- The same procedures as in Example 5 were repeated fivetimes except that the chelate compound was prepared from 0.01 1 g(0.00004 mole) of iron (11) sulfate heptahydrate and 0.002 g (0.000018mole) of catechol in 87 ml of water adjusted with sulfuric acid to pHsof 1.9 (Example 30), 2.5 (Example 31), 3.5 (Example 32), 4.0 (Example33) and 5.0 (Example 34) at a temperature of 45C, 0.106 mole of phenolin 14.3 ml of phenol aqueous solution was oxidized with 0.0266 mole ofhydrogen peroxide by adding dropwise, an aqueous hydrogen peroxidesolution over a 5 minutes period, and the reaction admixture was stirredfor 25 minutes after ,the addition of the aqueous hydrogen peroxidesolution was completed.

Table 11 shows the results.

From Table 1 1, it is observed that in thepHrange of 1.9 to 5.0, theyield ratio of catechol to hydroquinone varies.

EXAMPLES 35 THROUGH 41 The same operations as in Example 5 were repeatedseven times except that the chelate compound was prepared from 0.01 1 g(0.00004 mole) of iron (11) sulfate heptahydrate and 0.00004 mole of aligand compound selected from the group consisting of B-alanine (Exam- 11 ple 35), o-phenanthroline (Example 36), isocinchomeronic acid (Example37), nicotinic acid (Example 38), nicotinic amide (Example 39),a-thiophenic acid (Example 40) and 2,2,2"-trihydroxyethylamine (Example41 in 87 ml of water at a pH of 3.0, 0.106 mole of phenol in 14.3 ml of70% phenol aqueous solution Table 13 was oxidized by adding in drops, anaqueous solution containing 0.0266 mole of hydrogen peroxide over a 5Yield (g) 32 1 f 2f; minutes period, and the reaction admixture wasstirred catechol hydmquinone for minutes after the addition of theaqueous hydro- 10 Process y 10 hy based on 2 2 No. Cateehol qumonequmone used (71) gen peroxide solution was completed.

Table 12 shows the results. 7 0743 Table 12 Yield Sum of fields Yield(g) ratio of of catechol catechol and hydroto quinone based Ex.Hydrohydroon H 0 used No. Ligand Catechol quinone quinone (72) 35B-Alanine 1.04 0.665 1.56 58.3

' Phenanthroline 1.03 0.71 l 1.45 59.5

37 Isocinchomeronic acid 0.989 0.673 1.47 56.8

38 Nicotinic acid 0.946 0.635 1.49 54.0

39 Nicotinic amide 1.05 0.722 1.46 60.6

40 a-Thiophenic acid 1.07 0.708 1.51 60.8

41 2,2'.2"-trihydroxyethyl 0.995 0.639 1.56 55.8 amine 8 1.03 0.740 1.3960.5 9 1.06 0.755 1.40 62.0 10 1.03 0.732 1.41 60.2 40 EXAMPLE 42 12.5ml of a 80% aqueous phenol solution containing 0.106 mole of phenol, and0.014 g (0.00005 mole) of iron (II) sulfate heptahydrate and 0.0055 g(0.00005 mole) of eatechol were added to 84.5 g of water which had beenadjusted with sulfuric acid to a pH of 3.5. The admixture thus preparedwas changed into a heatinsulated reaction vessel and heated to atemperature of 45C. At this temperature, a 30% hydrogen peroxide aqueoussolution containing 0.0266 mole of hydrogen peroxide was added to theadmixture within 1 minute. The oxidation of the phenol startedimmediately while rapidly generating heat. The temperature of thereaction admixture reached a maximum about 59C about 10 minutes afterthe addition of the aqueous hydrogen peroxide aqueous solution wascompleted. When the temperature of the reaction admixture reached themaximum point, the reaction was completed. The resultant catechol andhydroquinone and the unreacted phenol were extracted with 200 g ofn-butyl acetate in the same manner as in Example 1. The extractionresidue contained the chelate compound, catechol iron (11) and had atemperature of 45C.

The same process as mentioned above was repeated 9 times except thatphenol and hydrogen peroxide in the same amounts as those mentionedabove were added to the extraction residue obtained in the precedingprocess, without heating the reaction admixture.

Table 13 shows that the chelate compound, catechol iron (11), can berepeatedly used as the catalyst without a decrease in catalytic activitythereof.

EXAMPLES 43 AND 44 AND COMPARISON EXAMPLES 3 AND 4 In Example 43, thesame operations as in Example 1 were repeated except that 0.011 g(0.00004 mole) of iron (II) sulfate heptahydrate, 0.002 g (0.000018mole) of catechol and 14.3 ml of phenol aqueous solution were added intoml of water which had been adjusted to a pH of 3.5 with sulfuric acid,at a temperature of 20C. Thereafter, 3.01 g of a 30% hydrogen peroxideaqueous solution containing 0.0266 mole of hydrogen peroxide was addedby drops, over a period of 5 minutes into the admixture prepared above,while stirring. The reaction admixture was further stirred for 25minutes after the addition of the aqueous hydrogen peroxide solution wascompleted.

In Comparison Example 3, the same operations as in Example 43 wererepeated using no catechol.

In Example 44, the same operations as in Example 43 were carried outusing iron (II) sulfate heptahydrate in an amount of 0.11 g (0.0004mole).

In Comparison Example 4, the same procedures as in Example 44 wererepeated using no catechol.

The results are shown in Table 14.

Table 14' 4 Sum of yields of Yield catechol lron ratio 1 and (11) Yield(g) of hydrosulfate catechol quinone Examheptato based on ple hydrateHydrohydro- H O No. (g) Catechol Catechol qui quinone used (71) none 43added 0786 0.256 3.07 35.6

0.01 1 Comp. none 0.613 0.235 2.61 29.0

44 added 1.00 0.643 1.56 56.2

0.1 1 Comp. none 0.891 0.568 1.57 49.9

Table 14 clearly shows that the chelate compound,

catechol iron (11) promoted the production of catechol 20 EXAMPLES 45AND 46 AND COMPARISON EXAMPLES AND 6 25 In Example 45, the sameoperations as in Example 42 were repeated except that 12.5 ml of the 80%phenol aqueous solution containing 0.106 mole of phenol, 0.014 g(0.00005 mole) of the iron (11) sulfate heptahytion admixture. Thereaction admixture reached a maximum temperature of 37C about minutesafter the complete addition of the aqueous hydrogen peroxide solutionand reaction was completed.

In Comparison Example 6, the same operations as in Example 46 werecarried out using no catechol.

No heat generation was observed even 60 minutes after the completeaddition of the aqueous hydrogen peroxide solution. This indicates thatsubstantially no reaction occurred.

Table shows the yields of catechol and hydroquidrate and 0.003 g ofcatechol were added to 84.5 g of none in the above examples andcomparison examples.

water which had been adjusted with sulfuric acid to a pH of 1.6. As theaqueous hydrogen peroxide solution was added, the temperature of thereaction admixture 50 was completed.

In Comparison Example 5, the same process as in Example 45 was repeatedusing no catechol. Heat-generation was observed about 9 minutes aftercompletion of the addition of the aqueous hydrogen peroxide solution,and the temperature of the reaction admixture reached a maximum point of58C about 11 minutes after the completion of the addition, and at thattime, the reaction was completed.

In Example 46, the same procedures as in Example 45 were carried outexcept that the water was acidified to a pH of 1.7 and initially had atemperature of 20C, and catechol was used in an amount of 0.005 g.

The addition of the aqueous hydrogen peroxide solution immediatelycaused heat-generation in the reac- Table 15 shows that the chelatecompound, catechol iron (11) was more effective for promoting theproduction of catechol and hydroquinone that iron (11) sulfate,especially, at a low temperature.

EXAMPLE 47 This example relates to a method wherein catechol andhydroquinone were produced by adding a chelate compound to a mixture ofphenol and hydrogen peroxide.

11.3 g (0.12 mole): of phenol and 3.4 g of a 30% hydrogen peroxideaqueous solution containing 0.03 mole of hydrogen peroxide were added toml of water which had been adjusted to a pH of 3.5 with sulfuric acid,at a temperature of 50C. 5 ml of aqueous solution containing a chelatecompound which had been prepared from 0.014 g (0.00005 mole) of iron(11) sulfate heptahydrate and 0.0055 g (0.00005 mole) of catechol, wereadded to the admixture prepared above. After the addition was completed,the reaction admixture was stirred for 20 minutes. The resultantcatechol and hydroquinone were isolated by the same method as in Example1.

Table 16 shows the results.

Table 16 16 mole of 8-hydroxyquinoline (Example 55) and 0.0000 54 moleof ethylencdiaminetetraacctic acid (EDTA) (Example 56).

In Example 56, the pH of the chelate compound aqueous solution wasadjusted to 3.5 by adding a small Yeld (g) sum yelds of amount ofN-sodium hydroxide aqueous solution.

Yield ratio of catechol and a camchoi 1o hydroquinone based in everyexample, the temperature of the reaction ad- Catechol Hydroquinonehydroquinone on H2O2 used 71) mixture r6ached a maximum point 0f 6 to65C L13 0790 1.49 597 within minutes after the addition of aqueoushydrogen peroxide solution was completed, and at this temperature, thereaction was completed.

The yields of catechol and hydroquinone in every ex- EXAMPLES 48 AND 49ample are indicated in Table 18.

Table 18 Ligand Yield (g) Sum of yields of I catechol and Yield ratio ofhydroquinone Example Amount Hydrocatechol to based on H202 No. Name(mole) catechol quinone hydroquinone used ("/1) 50 Salicylic aldehyde0.000054 0.963 0.688 n 1.40 57.5 51 o-Arninophenol 0.000040 0.963 0.6641.45 56.7 52 Salicyclic acid 0.000054 0.965 0.643 1.50 56.0 53o-Nitrophenol 0.000081 0.919 0.676 1.36 55.6 54 Pyridine 0.000168 0.9180.665 1.38 55.1 55 S-Hydroxyquinoline 0.000054 0.970 0.703 1.38 58.3 56EDTA 0.000054 0.877 0.613 1.43 51.9

Note: EDTA; Ethylenediaminetctruacetic acid I The same operation as inExample 42. were repeated EXAMPLE 57 twice using, instead of iron (11)sulfate heptahydrate, 0.010 g (0.00005 mole) of iron (11) chloridetetrahydrate (Example 48) and 0.0135 g (0.00005 mole) of iron (Ill)chloride hexahydrate (Example 49). In every example, vigorous heatgeneration was observed just when the hydrogen peroxide was added to theadmixture of the chelate compound and phenol in water. Three minutesafter completion of the hydrogen peroxide addition, the reactionadmixture reached a maximum temperature of about 59C, and the reactionwas EXAMPLES 50 THROUGH 56 In Example 50, the same operations as inExample 42 were repeated except that 0.0066 g (0.000054 mole) ofsalicylic aldehyde was used instead of catechol, iron (ll) sulfateheptahydrate was employed in an amount of 0.015 g (0.000054 mole) andthe reaction admixture had an temperatures of 50C at the start of thereaction. I V

The same operations as in Example 50 were repeated six timesrespectively using, instead of sulicylic aldehyde, 0.000040 mole ofo-aminophenol (Example 51 0.000054 mole of salicylic acid (Example 52),0.000081 mole of o-nitrophenol (Example 53), 0.000168 mole of pyridine(Example 54), 0.000054 A chelate compound aqueous solution was preparedby by adding 6.00 g (0.0225 mole) of chromium (Ill) chloride hexahydrateand 0.166 g (0.00108 mole) of thiosalicylic acid into 86.5 g of waterand adjusting the mixture to a pH of 3.5 with an aqueous N-ammoniasolution. 13.68 ml of 80% phenol aqueous solution containing 0.1 16 moleof phenol was added to the chelate compound aqueous solution and theadmixture was adjusted to a temperature of 60C. At this temperature, 3.0ml of aqueous hydrogen peroxide solution containing 0.0291 mole ofhydrogen peroxide was added to the admixture within 1 minute. Theaddition of aqueous hydrogen peroxide solution immediately caused heatgeneration in the reaction admixture and the temperature of the reactionadmixture was elevated to a maximum point of 70C. The reaction admixturewas stirred at to C for 25 minutes after the addition of the hydrogenperoxide was completed.

The resulted catechol and hydroquinone were isolated and determined bythe same method as in Example 1.0.714 g of catechol and 0.660 g ofhydroquinone were obtained. The yieldratio of catechol to hydroquinonewas 1.08 and the sum of yields of catechol and hydroquinone was 42.9%based-on the amount in moles of hydrogen peroxide used.

EXAMPLES 58 THROUGH 62 In Example 58, a chelate compound aqueoussolution was prepared by adding 6.00 g (0.0213 mole) of cobalt v "(11)sulfate heptahydrate and 0.099 g (0.0009 mole) of catechol into 86.5 gof water and adjusting the mixture 5 g to a pH of 3.0 with a 2N-sulfuricacid aqueous solution.

a 30% hydrogen peroxide aqueous solution containing 0.0291 mole ofhydrogen peroxide was added to the admixture within 1 minute and,thereafter, the reaction 17 admixture was stirred at a temperature of 70to 80C for 30 minutes.

The resultant catechol and hydroquinone were isolated and determined bythe same method as in Example 1. The same operations as in Example 58were repeated using, iristead of catechol, 0.124 g (0.0009 mole) ofsalicylic acid (Example 59), 0.100 g (0.000540 mole) of isocinchomeronicacid (Example 60), 0.100 g (0.000999 mole) of 2-aminothiazole (Example61) and 0.100 g (0.00109 mole) of thioglycollic acid (Example 62).

Table 19 shows the results.

. 18 The same procedures as in Example 63 were repeated six times usingrespectively, instead of salicylic amide, 0.00126 mole of pyridine(Example 64), 0.000689 mole of'8-hydroxyquinoline (Example 65), 0.000598mole of mercaptobenzothiazole (Example 66), 0.00133 mole ofthioacetamide (Example 67), 0.00131 mole of thiourea (Example 68),0.000861 mole of dimethylglyoxime (Example 69). It should be noticedthat in each of Examples 63, 66 and 69, the reaction admixture werecharged into a heat-insulated reaction vessel and adjusted to atemperature of 45C at the start of the reaction.

The results are shown in Table 20.

Table 19 Table Ligand Yield (g) Sum of yields of catechol and Yieldratio of hydroquinone Example Amount Hydrocatechol to based on H2O2 No.Name (mole) Catechol quinone hydroquinone used (71) 63 Salicylic amide0.000729 1.008 0.660 1.53 52.1 64 Pyridine 0.00126 0.909 0.692 1.31 50.065 8-Hydorxyquinoline 0.000689 0.862 0.683 1.26 48.3 66 Mercapto-0.000598 0.777 0.547 1.42 41.4

' benzothiazole 67 Thioacetamide 0.00133 0.665 0.484 1.37 35.9 68Thiourea 0.00131 0.602 0.464 1.30 33.3 69 Dimethylglyoxime 0.0008610.746 0.573 1.30 41.2

Yield Sum f yields EXAMPLES 70 THROUGH 80 Yield ratio of of catechol gcatechol and hydro- In Example 70, the same operations as in Example 50E C t H d h 1 3 z were carried out using, instead of salicylic aldehyde,

x. aey roy ro- 2 ,use No. Ligand cho' quinone quinone 7 0.000054 mole ofanthramllc acid. 58 C t h I (H6 0705 I44 537 The same procedures as inExample 70 were re- 3 CC 0 59 salicylic 0965 0712 136 52A peated tentimes using respectlvely i nstead of anthraacid mllc acid, 0.000054 moleof orthanihc ac1d (Example ggfgjf 71 0.000054 mole of o-phenol sulfonicacid (Examacid ple 72), 0.000054 mole of a-nitroso-Bnaphthol (Ex- 250927 04577 501 ample 73), 0.000162 mole of a-picoline (Example 74), 6235;; 0986 5 I SL6 0.000162 moleof 2,6-lutidine (Example 75),0.000162collic acid mole of quinoline (Example 76), 0.000054 mole of 2- EXAMPLES63 THROUGH 69 hydroxyethylamine (Example 77), 0.000108 mole of ethylenecyanohydrin (Example 78), 0.000054 mole of oxamide (Example 79), and0.000081 mole of diethylene glycol (Example 80).

In Example 63, the same operations as in Example 57 Th results are Showni Table 21 Table 21 Ligand Yield (g) Sum of yields of catechol and 7Yield ratio of hydroquinone Example Amount Hydrocatechol 1.0 based on HO,

No. Name (mole) Catechol quinone hydroquinone used Anthranilic acid0.000054 0.931 0.651 1.43 55.1 71 Orthanilic acid 0.000054 0.941 0.6671.41 56.0 72 o-Phenol sulfonic acid 0.000054 0.923 0.650 1.42 54.8

73 a-Nitroso- B-naphthol 0.000054 0.945 0.685 1.38 56.8 74 a'Picoline0.000162 0.922 0.640 1.44 54.4 2,6-Lutidine 0.000162 0.954 0.654 1.4656.0 76 Quinoline 0.000162 0.940 0.65 3 1.44 5 5.5 77Z-Hydroxyethylamine 0.000054 0.982 0.706 1.39 58.8

78 Ethylene cyanohydrin 0.000108 0.924 0.684 1.35 56.0 79 Oxamide0.000054 0.967 0.706 1.37 58.3 0.000081 0.929 0.678 1.37 56.0

Diethylene glycol were carried out except that the coordinate compoundwas prepared from 1.00 g (0.00375 mole) of chromium (Ill) chloridehexahydrate and 0.100 g (0.000729 mole) of salicylic amide.

EXAMPLES 81 THROUGH 85 In Example 81, the same procedures as in Example57 were carried out except that the chelate compound 19 aqueous solutionwas prepared by adding 0.000200 mole of copper (11) sulfate pentahydrateand 0.000400 mole of glutamic acid into 91.5 g of water and adjusting atthe start of the reaction the mixture to a pH of 3.0 and a temperatureof 70C.

Further, the same procedures as in Example 81 were repeated four timesusing respectively, instead of glutamic acid, lysine (Example 82),methionine (Example 83), glycine (Example 84) and arginine (Example 85).

The pH of the chelate compound aqueous solution was 2.65 in Example 82,2.32 in Example 83, 2.55 in Example 84 and 3.0 in Example 85.

The results are shown in Table 22.

COMPARISON Example 7 An oxidation of phenol with hydrogen peroxide wascarried out without addition of an organic ligand compound.

7.5 g (0.0797 mole) of phenol and 0.675 g (0.00243 mole) of iron (11)sulfate heptahydrate were added to 110 ml of water which had beenadjusted to a pH of 3.6

LII

by adding sulfuric acid, and the mixture was cooled with ice to atemperature lower than 5C. 90 ml of an 1% by weight hydrogen peroxideaqueous solution containing 0.0265 mole of hydrogen peroxide was addedto the cooled mixture. The reaction admixture was stirred for 24 hours.The resulting catechol and hydroquinone were isolated and determined bythe same method as in Example 1. 1.136 g of catechol and 0.626 g ofhydroquinone were obtained. The ratio of the yield of catechol to thatof hydroquinone was 1.81 and the sum of the yields in moles of catecholand hydroquinone to the amount in moles of hydrogen peroxide used was60.5%.

What we claim is: l. A method for preparing catechol and hydroquinone,comprising the steps of:

oxidizing phenol with 10 to 100 percent by mole based on the amount bymole of said phenol, of hydrogen peroxide in an aqueous medium at atemperature of 10 80C. at a pH not higher than 6.0 in the presence of acatalyst consisting of at least one organic metal coordinate compoundwhich consists of at least one organic ligand componentcoordinate-bonded with at least one metal atom component selected fromthe group consisting of iron, copper, chromium, and cobalt and selectedfrom the group consisting of (a) any aromatic chelating compoundselected from the group consisting of catechol, salicylic aldehyde,salicylic acid, thiosalicylic acid, o-aminophenol, salicylic amide,o-nitrophenol, anthranilic acid, orthanilic acid, 0- phenol sulfonicacid, and a-nitroso-B-naphthol, (b)

a heterocyclic monodentate coordinating compound selected from the groupconsisting 'of pyridine. picolinm. lutidincs and quinoline, (c) aheterocyclic polydentate coordinate compounds selected from the groupconsisting of nicotinic acid, nicotinic amidc, isocinchomeronic acid,a-thiophenic acid, o-phenanthroline, 2-mercaptopyridine,Z-aminothiazole, 8-hydroxyquinoline, mercaptobenzothiazole ande-caprolactam, and (d)aliphatic chelating compounds selected from thegroup consisting of ethylene diamine, D,L-d-alanine, D,L-B-alanine,2,2,2"-trihydroxyethylamine, thioglycollic acid, thioacetamide,thiourea, 2,3-dimercapto-l-propano1, ethylenediaminetetraacetic acid,dimethylglyoxime, 2-hydroxyethylamine, ethylene cyanohydrin, oxamide,diethylene glycol, glutamic acid, lysine, methionine, glycine andarginine, said catalyst being in an amount of one-thirty to 100 percentby mole calculated in terms of said metal component contained therein,based on the amount by mole of said phenol, and isolating the resultingcatechol and hydroquinone from said oxidation mixture.

2. A method according to claim 1 wherein said catalyst is a chelate ofcopper sulfate pentahydrate and catecho].

3. A method according to claim 1 wherein said catalyst is a chelateprepared from copper sulfate pentahydrate and D,L-B-alanine.

4. A method according to claim 1 wherein said catalyst is a chelateprepared from chromium sulfate heptahydrate and catechol.

5. A method according to claiml wherein said catalyst is coppernicotinate.

6. A method according to claim 1 wherein said catalyst iscopper-a-thiophenate.

7. A method according to claim 1 wherein said catalyst is a chelateprepared from copper sulfate pentahydrate and a member selected from thegroup consisting of o-phenanthroline, nicotinic amide, ethylene diamine,pyridine, thiosalicylic acid, 'D,L-a-alanine, and e -caprolactam.

8. A method according to claim 1 wherein said catalyst is a chelateprepared from iron sulfate heptahydrate and catechol.

9. A method according to claim 1 wherein said catalyst is a chelateprepared from iron sulfate heptahydrate and a member selected from thegroup consisting of B-alanine, o-phenanthroline, isocinchomeronic acid,nicotinic acid, nicotinic amide, a-thiophenic acid, and2,2',2"-trihydroxyethylamine.

10. A method as claimed in claim 1, wherein said oxidation is carriedout at a pH of l to 5.

11. A method as claimed in claim 1, wherein said oxidation temperatureis from 20 to C at the start thereof.

12. A method as claimed in claim 1, wherein the isolation of catecholand hydroquinone is effected by extracting with an organic solvent forcatechol and hydroquinone.

13. A method as claimed in claim 12, wherein said extracting organicsolvent is selected from the class consisting of methyl isobutyl ketone,n-butyl acetate and isopropyl ether.

1. A METHOD FOR PREPARING CATECHOL AND HYDROQUINONE, COMPRISING THESTEPS OF: OXIDIZING PHENOL WITH 10 TO 100 PERCENT BY MOLE BASED ON THEAMOUNT BY MOLE OF SAID PHENOL, OF HYDROGEN PEROXIDE IN AN AQUEOUS MEDIUMAT A TEMPERATURE OF 10*-80*C. AT A PH NOT HIGHER THAN 6.0 IN THEPRESENCE OF A CATALYST CONSISTING OF AT LEAST ONE ORGANIC METALCOORDINATE COMPOUND WHICH CONSISTS OF AT LEAST ONE ORGANIC LIGANDCOMPONENT COORDINATE-BONDED WITH AT LEAST ONE METAL ATOM COMPONENTSELECTED FROM THE GROUP CONSISTING OF IRON, COPPER, CHROMIUM, AND COBALTAND SELECTED FROM THE GROUP CONSISTING OF (A) ANY AROMATIC CHELATINGCOMPOUND SELECTED FROM THE GROUP CONSISTING OF CATECHOL, SALICYLICALDEHYDE, SALICYLIC ACID, THIOSALICYLIC ACID, O-AMINOPHENOL, SAICYLICAMIDE, O-NITROPHENOL, ANTHRANILIC ACID, ORTHANILIC ACID, O-PHENOLSULFONIC ACID, AND A-NITROSO-BNAPHTHOL, (B) A HETEROCYCLIC MONODENTATECOORDINATING COMPOUND SELECTED FROM THE GROUP CONSISTING OF PYRIDINE,PICOLINES, LUTIDINES AND QUINOLINE, (C) A HETEROCYCLIC POLYDENTATECOORDINATE COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF NICOTINICACID, NICOTINIC AMIDE, ISOCINCHOMERONIC ACID, A-THIOPHENIC ACID,O-PHENANTHROLINE, 2-MERCAPTOPYRIDINE, 2-AMINOTHIAZOLE,8-HYDROXYQUINOLINE, MERCAPTOBENZOTHIAZOLE AND E-CAPROLACTAM, AND(D)ALIPHATIC CHELATING COMPOUNDS SELECTED FROM THE GROUP CONSISTING OFETHYLENE DIAMINE, D,L-A-ALANINE, D,L-B-ALANINE,2,2'',2"-TRIHYDROXYETHYLAMINE, THIOGLYCOLLIC ACID, THIOACETAMIDE,THIOUREA, 2,3-DIMERCAPTO-1PROPANOL, ETHYLENEDIAMINETETRAACETIC ACID,DIMETHYLGLYOXIME, 2-HYDROXYETHYLAMINE, ETHYLENE CYANOHYDRIN, OXAMIDE,DIETHYLENE GLYCOL, GLUTAMIC ACID, LYSINE, METHIONINE, GLYCINE ANDARGININE, SAID CATALYST BEING IN AN AMOUNT OF ONE-THIRTY TO 100 PERCENTBY MOLE CALCULATED IN TERMS OF SAID METAL COMPONENT CONTAINED THEREIN,BASED ON THE AMOUNT BY MOLE OF SAID PHENOL, AND ISOLATING THE RESULTINGCATECHOL AND HYDROQUINONE FROM SAID OXIDATION MIXTURE.
 2. A methodaccording to claim 1 wherein said catalyst is a chelate of coppersulfate pentahydrate and catechol.
 3. A method according to claim 1wherein said catalyst is a chelate prepared from copper sulfatepentahydrate and D,L- Beta -alanine.
 4. A method according to claim 1wherein said catalyst is a chelate prepared from chromium sulfateheptahydrate and catechol.
 5. A method according to claim 1 wherein saidcatalyst is copper nicotinate.
 6. A method according to claim 1 whereinsaid catalyst is copper- Alpha -thiophenate.
 7. A method according toclaim 1 wherein said catalyst is a chelate prepared from copper sulfatepentahydrate and a member selected from the group consisting ofo-Phenanthroline, nicotinic amide, ethylene diamine, pyridine,thiosalicylic acid, D,L- Alpha -alanine, and epsilon -caprolactam.
 8. Amethod according to claim 1 wherein said catalyst is a chelate preparedfrom iron sulfate heptahydrate and catechol.
 9. A method according toclaim 1 wherein said catalyst is a chelate prepared from iron sulfateheptahydrate and a member selected from the group consisting of Beta-alanine, o-phenanthroline, isocinchomeronic acid, nicotinic acid,nicotinic amide, Alpha -thiophenic acid, and2,2'',2''''-trihydroxyethylamine.
 10. A method as claimed in claim 1,wherein said oxidation is carried out at a pH of 1 to
 5. 11. A method asclaimed in claim 1, wherein said oxidation temperature is from 20 to70*C at the start thereof.
 12. A method as claimed in claim 1, whereinthe isolation of catechol and hydroquinone is effected by extractingwith an organic solvent for catechol and hydroquinone.
 13. A method asclaimed in claim 12, wherein said extracting organic solvent is selectedfrom the class consisting of methyl isobutyl ketone, n-butyl acetate andisopropyl ether.